Continuous-operation device for treatment of leather and similar materials

ABSTRACT

A continuous-operation device for the treatment of a leather piece and similar materials, comprising a work station including a roller unit including a pair of rollers and through which the leather piece is moved, the work station including an inlet side and an outlet side, a traversing path upon which the leather piece is transversely moved, the traversing path extending from the inlet side and through the work station to the outlet side, a gripper for removal of the leather piece from one of the pair of rollers as the leather emerges from the work station outlet side, the gripper also for traversal movement of the leather piece after it emerges from the work station outlet side, a drive for driving the gripper, the gripper being operatively connected to the work station outlet side and movably mounted on the drive.

The invention relates to a continuous-operation device for the treatmentof leather and similar materials, in particular a printing, dyeing,smoothing, or dewatering device, with a traversing path that extendsthrough at least one roller unit, especially a pair of rollers. Suchcontinuous-operation devices are frequently and widely used in tanningand leather working. Conveyor, vacuum, and pressure equalization belts,or similar endless-loop flexible elements often extend along thetraversing path between the surfaces of the roller pair on the outletside or, if applicable, of upstream roller pairs.

In the discharge area of the roller unit, the emerging edge area of theleather pieces adhere more or less strongly to a roller surface or tothe surface of a revolving belt extending through the roller pairinvolved. For the sake of simplicity, a roller surface will be referredto exclusively in this context in the following discussion.

Generally speaking, the problem arises of quickly and reliably releasingthe edge area of the emerging leather pieces from the roller surface towhich the leather adheres so that the continuous operation process willnot be impeded and the leather will not be damaged. Hence the problem tobe solved by the invention is creation of continuous operation devicesof the type referred to in the foregoing that permit such separation ofthe leather from the roller outlet in continuous operation.

SUMMARY OF THE INVENTION

This problem is solved by the two alternative embodiments of the presentinvention, which in principle are to be used separately but if desiredcan be applied advantageously together in appropriate combinations. Theyare based on a common inventive concept. Among other things, thisconcept involves keeping at least the sensitive grain side of theleather free from relative movement with respect to machine elements,that is, from undesirable sliding or frictional application, and thusfrom damage, during the process of emergence over the length of theleather piece, inside the leather surface, except at most in the narrowarea of the emerging edge. This is particularly important in the case ofcontinuously operating staining and imprinting machines, inasmuch as thegrain or outer side of the leather just provided with stain is stillsensitive to pressure. Both the pulling of the leather by drivengripping means and the release by means of compressed air jets provideoptimum satisfaction of these operational requirements. The firstembodiment is especially well suited for leather having surfacesdifficult to separate from the roller.

Other objects and advantages of the present invention will become moreapparent to those persons having ordinary skill in the art to which thepresent invention pertains from the following description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a leather staining machine of the presentinvention.

FIG. 2 is a plan view of the embodiment of FIG. 1.

FIG. 3 is a partial longitudinal section of the gripping means of theembodiment of FIGS. 1 and 2.

FIG. 4 is an enlarged side view of the roller discharge area of theembodiment of FIGS. 1 through 3.

FIG. 5 is a schematic diagram of the control process of the embodimentof FIGS. 1 through 4.

FIG. 6 is a second operating situation wherein the gripping means is inthe waiting position.

FIG. 7 is a front view of a second embodiment of the present invention.

FIG. 8 is a side view of the embodiment of FIG. 7.

FIG. 9 is a third embodiment of the present invention.

FIG. 10 is an enlarged view of the embodiment of FIG. 9.

FIG. 11 is an enlarged sectional view of the embodiment of FIGS. 9 and10 showing the distribution of gripping means over the roller.

FIG. 12 is an enlarged side view of the roller of FIGS. 9, 10 and 11.

FIG. 13 is a view of the embodiment of FIGS. 9 through 12 showing thepunching element in the inactive state.

FIG. 14 is a view of the embodiment of FIGS. 9 through 12 showing thepunching element in the active state.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a leather staining machine is shown designedas a continuous operation machine, with a continuous path for leatherpieces L extending in the direction of arrow P1 through a roller unit(10). The roller unit comprises an upper stain roller 11 with staintrough 12 and a lower counterpressure and transfer roller 13 acrosswhich a transition belt TA extends. The upper side of transition belt TAforms a bearing surface AF for the leather pieces to be fed. In thesituation shown in FIG. 1, the leading edge K of a leather piece hasreached the outlet side of the roller unit. Gripping means 20 aremounted here for removal of the emerging leather pieces. These grippingmeans 20 are movably mounted in the direction of passage and areconnected to drive means 70 that act in the direction of extraction ofthe leather pieces. As is to be seen from FIG. 1, a lower positionedoutlet conveyor belt TB connected to the discharge area of the rollerunit extends in direction P1 to the end of the machine on the outletside.

During operation, the emerging edge of the leather K is released by thegripping means from the surface of the belt to which the leather more orless strongly adheres, that is, generally speaking from the surface ofthe stain roller, and is gripped by these means. The drive means 70 arethen activated and the gripping means 20 pull the edge of the leather insynchronization with the speed of discharge of the leather at the outletfrom the roller unit as the leather is progressively released from thesurface of the conveyor belt or roller in direction P1 to an assignedend position, for example, into the area of the end of the machine onthe outlet side. In the process, the central area of the length of theleather piece subsides onto the conveyor belt TB, which is driven insynchronization with the drive means 70. Hence the leather, which isstill damp with stain and is sensitive, is spread out gently and free offolds, ready for removal.

In the example shown, the gripping means comprise four gripping means 20that are arranged across the operating width of the roller unit 10 andthat grip the edge area K of the emerging leather pieces. As FIG. 2shows, there is provided for each gripper inside the drive means 70 astripping and driving device 71, 72, 73, or 74 that may be activatedindividually, in the form of a compressed air cylinder that extends moreor less over the useful length of the conveyor belt TB.

A compressed air cylinder such as this, 71 for example, is ofcommercially available design; a partial longitudinal section of acylinder is shown in FIG. 3. Accordingly a double acting piston 80 ismounted in a cylindrical jacket 81 that is provided with a slit in thejacket 82 extending parallel to the axis. Pressure chambers 80a, 80b onboth sides of the piston are sealed off from the exterior by a softelastic sealing element 83 that extends over the length of the slit inthe jacket 82 and itself has a longitudinal slit 83, and are sealed offfrom each other by means of a sealing slide 84 fastened on the piston.Longitudinal slit motion seals for piston and cylinder systems areuniversally known and need no special explanation here. An angularsupport element 85 and a coupling element 86 connect the gripper 22 tothe piston. Alternate pressure loading of the cylinder results in ashuttle type mode of operation, specifically, the stripping movement ofthe individual grippers, already explained, along the conveyor belt TBin the direction of arrow P1, and return movement in the oppositedirection, that of P1a.

It goes without saying that a common strip and drive device can ifdesired be provided for a plurality of grippers.

An essential feature of the invention in this context is that, as isshown in FIG. 2, at least one gripper 22 or at least one gripper groupis adjustably mounted in direction P2 transversely to direction ofpassage P2, within the operating width of the roller unit 10. In theexample shown, the two outer grippers are assembled together with theirdrive devices 71 and 74 to form a laterally adjustable modular unit.

For this purpose, the pertinent compressed air cylinders are slidablymounted on rails 31, independently of each other, inside a framelikerack element 30, and each is coupled to a selectively activatedtransverse adjustment device 32 or 34 in the form of a compressed aircylinder. In addition, a transverse control device 40 is provided with aprogram control unit that has a plurality of predetermined andoptionally activatable transverse position adjustments 1 to 4 and 5 to 8inside the operating width of the roller unit. The transverse controldevice 40 is mounted as a structural group resembling a cross-arm withupper transverse adjustment selection keys and mounted conveniently foroperation above the leather application surface AF.

The points of application of the stripping forces along the emergingedge of the leather can accordingly be adapted to different outercontours and qualities of the leather pieces to be worked. If desired, alarger number of grippers may of course be provided and preferably maybe designed so as to be laterally adjustable, either individually or ingroups.

As may be seen from FIG. 3, several position detectors ST0, STW, STZ,and STE are mounted on the compressed air cylinder and are coordinatedwith specific positions of the piston 80, that is, with the pertinentgripping means 20 as well, along their path of movement. These positiondetectors are activated by the piston 80 to generate a control signal,in the example of a dual logic signal one having the value 1, when themidpoint of the length of the piston reaches the switching position ofthe pertinent detector, as indicated by the broken line. Conventionalinductance proximity switches, for example, are used for the positiondetectors, the piston being provided in the usual commercial versionwith a control magnet installed at the midpoint of its length. Thedetectors are associated with respect to the gripping means 20 with aninitial position on the roller outlet (ST0), a waiting position (STW),anintermediate position (STZ), and an end position (STE). Thesedetectors, and STZ and STE in particular, can be installed so as to beadjustable along the path of movement of the gripper. This arrangementof detectors serves the purpose of control of the forward movement orstripping movement and the return travelmovement; this control remainsto the explained in what follows.

FIG. 4 shows, on a larger scale, a section of the roller discharge areafrom FIG. 1 and a gripper 22 in the initial position ST0 (for the sakeof clarity, the gripper movement positions will be identified by thedesignations ST0, STW, STZ, and STE of the corresponding positiondetectors, inasmuch as the invariable longitudinal displacement betweengripper and piston mid-length is negligible). The tonglike structure ofthe gripper 22, with clawlike gripping elements 23, 24 that can be movedfrom an open position and a closed position (indicated by broken lines)is illustrated in the drawing. The gripping elements have a tip areadesigned as strippers 25, which, when the gripping elements are in theopen position illustrated, with the grippers in the open position ST0,that is, in the initial position for the gripping operation, arepositioned in the immediate vicinity of an associated conveyor surfaceTO of the rollers 11, 13 (that is, of the feed belt TA not shown here).The leather edge area that on emergence generally adheres to a conveyorbelt or roller surface is thus in each instance reliably freed by one ofthe strippers 25 and reaches the area between the open gripping elements23, 24. This situation is illustrated by solid lines in FIG. 3.

Each gripper is associated with a detector LD that detects entry of theleather edge area into the space between the opened gripping elementsand triggers immediate closing of these elements. For simpleapplications, such as stiff leather or an emerging leather edge ofuncomplicated outline, the configuration costs may be lowered byproviding a leather presence detector for individual grippers only, orin an extreme case for only one gripper.

In the example under discussion, an optoelectronic detector with a lightemitter LD1 and a light sensor LD2 are provided. The scanning beam pathS, indicated by a broken line, extends from the emitter LD1 to a firstreflecting surface SP1 mounted on the inner front side of thetransparent gripping element 23, thence through the interior of thegrippers to the also transparent gripping element 24 to a secondreflecting surface SP2 mounted inside the latter, to the sensor LD2.Mounted on the gripper is a feed and control unit 60, shown here inschematic form only, that supplies power in the conventional manner overlines 6 to the emitter and processes the output signals of the sensor. Apositioning device 50 of conventional design, also indicated onlyschematically by broken lines, with a suitable servomotor, receives acontrol pulse from the feed and control unit 60 and causes the grippingelements to close along arrows P3 as indicated by broken lines. As is tobe explained in greater detail below, after a brief delay that ensuresfirm gripping of the leather edge, detection of the presence of leathertriggers advance of the grippers as indicated by arrow P1.

The detection of the presence of leather as described in the foregoingis associated with the individual grippers or groups of grippers. Inaddition, a detection device GD is present as shown by FIGS. 2 and 4.This device extends over the entire width of the roller discharge area,or a part of this area, monitoring this total area for the presence ofmaterial or freedom from emerging material. In the example underdiscussion, this device comprises a series, extending over the operatingwidth, of light emitters GD1 mounted above the exit plane, together withpertinent sensors GD2 that are mounted below this plane. The pertinentscanning beam path s thus penetrates the plane of the material. Thespacings and the position of the scanning units consisting of emittersand sensors are so selected that sufficiently constant coverage of thematerial is achieved. A particular achievement of this solution is thatthe scanning beams pass over the grippers 22 while they are in theirinitial position. However, the progress of movement can generally bereadily designed so that even masking of scanning beams by the grippersis no disruptive factor, inasmuch as this masking can occur only in theinitial position. As is indicated in FIG. 4, the sensor output signalsof the scanning units, specifically, a logical 1 for the presence ofmaterial, are coordinated in a NOR logic unit GL. Hence an output signalof the latter, X, representing the value 1 has the meaning "rollerdischarge area is free of material."

The control process will now be explained with reference to the logicsystem diagram in FIG. 5.

The drive control means 100 indicated here in the form of a generaldiagram comprise control channels 101 to 104 that are associated withdrive devices 71 to 74. Logic unit GL already referred to delivers itssignal X and the inverted signal X' to a distributor VT to which controlchannels 101 to 104 are connected. The basic structure of controlchannel 71 is illustrated; the remaining ones are of the same structureand are indicated merely by their reference number at the distributorVT. Channel 101 with its associated functional groups is described inwhat follows; the description applies correspondingly to the otherchannels.

Drive device 71 is indicated as a functional unit with control inputs Vfor "forward movement" (stripping direction) and R for "returnmovement." These inputs can be triggered alternatively and areinterlocked by conventional means (not shown). The gripper control means60 and gripper positioning means 50 are also indicated as functionalunits. They are interconnected by control inputs ZO with the function"open grippers" and ZS for "close grippers" associated with thepertinent signal value logical 1. The gripper control means 60 include aleather presence detector LD locally associated with the pertinentgripper, which detector, as has already been pointed out, generates acontrol signal having the value of logical 1 if material is present inthe interior space of the grippers.

The circuitry illustrated includes biflops (flipflops) FF0, FF1, and FF2as signal storage elements that in the initial state assume theirpreferred logical state as indicated by "a." As is indicated in thecircuit diagram, biflops are involved; they respond to positive inputsignals only. The remaining elements are mentioned in the description ofoperation.

Assume that the device is in the initial state as shown in FIGS. 1 and4; the edge of the leather K has not yet left the roller outlet(differing in this respect from the situation shown in FIG. 4). Aleather edge section now enters the pertinent interior space of agripper, so that LD is activated and FF0 is set, that is, ZS isactivated with 1 and the gripper is closed by way of its positioningdevice 50. After a delay determined by safety considerations andexecuted by a timing element t1, FF1 is thereby set in control channel101, and the drive device is activated with control signal 1 at theinlet V to initiate forward movement.

In the initial position, the position indicator ST0 had ended thepreceding gripper return by generating an inhibit signal 1 by way of anAND blocking gate (inverting input) A1 at input R. The gripper movingforward now leaves ST0, and input R is freed to prepare for thesubsequent return movement, but is not yet activated because FF2 isstill in the reset state. In addition, GL now generates the signal X'=1,having the meaning "roller discharge area not free of leather," so longas the trailing area of the piece of leather passing through is still inthe roller area.

As long as an intermediate position indicator STZ remains inactivated asa result of opening of a pertinent monitoring switch WS and as long asthe signal X=0 persists, the gripper moves to its end position, and theposition indicator STE terminates forward movement by way of an OR gateby resetting FF1. FF0 and FF2 are reset at the same time, that is, onthe one hand the gripper is opened and on the other return travel of thegripper is initiated, through activation of R by way of the gate A1 thathas been released by ST0 in the meantime. The same occurs when theintermediate position is reached in the event of activation of STZ,because of the signal path assigned by way of WS and 01.

Assignment of the signal path to FF0, FF1, and FF2 by VT, by way of 01,results in opening of the grippers, termination of forward travel, andinitiation of return travel in the embodiment described, but this resultalso occurs when the trailing edge of the leather is leaving the rolleroutlet, before the gripper reaches the intermediate or end position, andaccordingly the signal X=1 is generated by way of GD and GL. In thiscase, then, when passage of a piece of leather has ended, all grippersare opened immediately and are returned to their initial position. Thismay result in significant saving of operating time.

Provision has also been made for a situation in which advance travel hasended and return travel has been initiated by the activated intermediateposition indicator STZ but the piece of leather has not yet left theroller outlet, so that movement of a gripper to its initial positioncould result in collision with the leather still present there. In thiscase the signal X'=1, which holds an output of the AND gate controllingthe output of waiting position indicator STW ready, persists during thegripper return travel initially proceeding as it did at first. If thegripper now reaches STW, the latter blocks return travel by way of A2and another OR gate 02 by resetting FF2. Hence the gripper initiallypersists in the waiting position and cannot collide with the leather. Anoperating situation such as this is shown in FIG. 6. The piece ofleather, a large part of whose surface rests on the conveyor belt TB, iscarried along by the conveyor belt despite the elimination of thestripping forces on the leading edge of the leather, and the trailingedge also finally leaves the roller discharge area, at which point GDand GL again deliver the signal X=1. The corresponding positive signaledge now sets FF2 again by way of 01 and initiates continuation of thereturn travel. The gripper, arriving at ST0, now for safetyconsiderations blocks the return travel over A1 directly by way of R,and also resets FF2. The entire system is thereby returned to itsinitial state.

FIG. 7 shows another embodiment of a leather staining machine, in theform of a front view of a roller unit corresponding more or less to thefirst embodiment. The direction of view is horizontal and toward thedischarge area of the roller unit. FIG. 8 shows a side view of theroller discharge area corresponding to that in FIG. 2 of the firstembodiment. In the version under discussion, a compressed air nozzleunit DSA is provided across the operating width of the roller outlet, inplace of mechanical stripping elements. In other respects elementscorresponding to the preceding embodiment are provided with the sameidentification symbols to the extent that this is necessary forunderstanding. As is to be seen from FIG. 8, the individual nozzles aremounted in the immediate vicinity of the surface of the roller 11 andare directed toward the adhering leather edge K. It is advisable tooperate with compressed air blasts that are to be triggered by detectiondevices as a function of arrival of the leather edge, analogously to thefirst embodiment. Significant conservation of compressed air is therebyachieved. As is also indicated by broken lines in FIG. 8, the releasedleather edge drops onto the conveyor belt TB under its own weight and iscarried away by the latter without grippers. However, it goes withoutsaying that, if desired, here as well grippers may be provided as in thefirst embodiment.

FIGS. 9 through 14 illustrate another embodiment of a continuousoperation device as claimed for the invention, again on a continuouslyoperating leather imprinting machine as an example of a work stationAST. In this instance as well the leather is pressed against the stainroller in the imprinting process by a mating roller W2 with a deliverybelt ZFB, and adheres relatively strongly to the surface of the rollerW1 because of the still liquid stain. Hence a discharge roller W3 withgripping means GR in the form of a grid distributed over thecircumference of the roller, which gripping means mechanically lift theleather, is provided on the outlet side of the pair of rollers. The dryside of the leather then rests on the roller W3 and slides from it ontoa removal belt AFB. The rollers W1 and W3 are synchronized by linkageKTR of conventional design, preferably with adjustable transmissionratio, as a function of their peripheral speeds. If desired, any givendifference in roller peripheral speeds may be set, for example, a slightlead of the removal roller.

FIG. 12 shows a transfer point between the rollers W1 and W3 on a largerscale. As is indicated diagrammatically here, the gripping means areprovided with punching or slotting elements SK designed so that they maybe shifted between an active state in which they are applied to theleather and an inactive state in which the leather is released. Apositioning device STE synchronized with the passage of the leather orwith rotation of the rollers is provided for activation and inactivationof the punching or slotting elements SK. As a result of coupling withthe roller W3, this positioning device STE causes shift of the punchingor slotting elements (generally referred to as pricking elements) SKbetween the active and the inactive state to be synchronized withpassage of these elements by the transfer point UST.

The gridlike distribution of the punching or slotting elements over thesurface of the roller W3 is shown in detail in FIGS. 11 and 12. For thepurpose of even separation of the leather from the stain roller, aprovision is made whereby the punching or slotting elements arranged ina row extending more or less in the longitudinal direction of therollers may be shifted together between an active and an inactive state.FIGS. 13 and 14 show on a larger scale a structural unit BEH with apunching or slotting element SK in the inactive state ZI and activestate ZA. In the embodiment exemplified, the punching or slottingelements SK are designed in the form of needles, and a common,preferably fluid operated, reversal device UVR is provided foractivation and inactivation for the punching or slotting elementsarranged in a row extending more or less in the longitudinal directionof the rollers. In the embodiment exemplified, the punching or slottingelements are mounted in a guide sleeve FHL so that they may be shiftedbetween the active and the inactive state and are placed under tensionby a repositioning spring in the direction of one of their operatingstates, preferably in the direction of the inactive state. It isadvantageous to give consideration also to a suitable swivel mount.

The common fluid operated reversal device UVR comprises at least onehose or bellows element SBE that acts on the punching or slottingelements in order to cause swivelling and that can be loaded with andrelieved of hydraulic fluid. This hose or bellows element SBE isdirected, for one row of punching or slotting elements, in alignedsupport pipes TRR that are fastened in longitudinal grooves in theroller jacket and conform to the shape of the latter, and that connectthe structural units BEH of one row to each other. Spacer pipes DSTsecure the structural units in place.

The elements SBE, which preferably are designed as simple andsufficiently flexible hoses, are connected by way of conventionalhydraulic fluid control means (accordingly not described in furtherdetail) to a source of hydraulic fluid. These control means comprise acontrol valve of conventional design that may be selectively activatedfor each row of punching or slotting elements. As it passes the transferpoint, the element SBE of the pertinent row is loaded with hydraulicfluid and thus expanded, for example, by a peripheral cam arrangement ofconventional design already contained in the synchronous positioningdevice already referred to and acting in conjunction with the shaft ofthe roller WE. Consequently, the punching or slotting elements of therow are transferred to their active state against the action of therepositioning spring RFD and are pressed into the nonsensitive reverseor flesh side of the leather. As the roller continues to rotate, theleather is then diverted into a direction tangential to thecircumference of the roller W3 and is accordingly separated from thestain roller W1. Immediately afterward the hose or bellows element SBEis relieved of pressure by the synchronous control unit, and thepunching or slotting elements release the leather and return to theinactive state.

It goes without saying that more or less any suitable conventionalhydraulic fluid or electromagnetic valve systems may be used forpurposes of control. Preference may be given to use of a compressed airdrive system to shift the punching or slotting elements, but appropriatehydraulic systems may also be used to advantage, depending on theservice conditions.

It is especially advantageous in the case of a compressed air system tohave a design such that the hollow body of a roller is connected to acompressed air line by way of a delivery coupling and serves as acompressed air storage unit.

We claim:
 1. A continuous-operation device for the treatment of aleather piece and similar materials, comprising:a work station includinga roller unit, said roller unit including a pair of rollers throughwhich said leather piece is moved, said work station including an inletside and an outlet side, a path upon which said leather piece is moved,said path extending from said inlet side and through said work stationto said outlet side, a gripping means for removal of said leather piecefrom one roller of said pair of rollers as said leather emerges fromsaid work station outlet side and for movement of said leather pieceafter it emerges from said work station outlet side, a drive means fordriving said gripping means, said gripping means being operativelyconnected to said work station outlet side and movably mounted on saiddrive means.
 2. The device as claimed in claim 1, said roller unithaving an operating width, said gripping means further including aplurality of grippers distributed over said roller unit operating width,said grippers gripping the edge of the leather piece.
 3. The device asclaimed in claim 2, further comprising a means for adjusting theposition of at least one of said plurality of grippers transverselyrelative to said path of said leather piece along said roller unitoperating width.
 4. The device as claimed in claim 3, wherein said meansfor adjusting the position of at least one of said plurality of gripperscomprises a selectively activated transverse adjustment deviceoperatively connected to said at least one of said plurality ofgrippers, and a selectively activated transverse control device having aplurality of assigned and transverse position settings for selectivelyactivating said transverse adjustment device.
 5. The device as claimedin claim 1, wherein said gripping means has at least one gripper, saidat least one gripper including a pair of tongs movable between an openposition and a closed position.
 6. The device as claimed in claim 5,wherein said roller unit includes an associated conveyor belt surfaceand said gripper includes at least one clawlike gripping element havinga stripper at a tip area thereof, said gripping element mounted in adischarge position near said roller unit conveyor belt surface.
 7. Thedevice as claimed in claim 1, wherein said gripping means is movablebetween an open position and a closed position, the device furthercomprising:at least one detecting means operatively connected to saidgripping means for establishing the presence of leather in the grippingarea, and a gripper control means for activating the closing and openingof said gripping means.
 8. The device as claimed in claim 5, furthercomprising at least one detecting means operatively connected to saidgripping means for establishing the presence of leather in the grippingarea, and a gripper control means for activating the closing and openingof said gripping means.
 9. The device as claimed in claim 8, furthercomprising at least one sensor unit for said at least one gripper forscanning the interior of said tongs.
 10. The device according to claim2, further comprising:a stripping and drive device provided forseparately driving a plurality of gripping means; and drive controlmeans for controlling said stripping and drive device, said drivecontrol means including a drive control channel for each of saidgripping means.
 11. The device according to claim 10, wherein saidstripping and drive device is reversible for return travel of saidgripping means, said drive control means activating return travel ofsaid stripping and drive device.
 12. The device according to claim 11,further comprising a detector device covering substantially theoperating width of said roller unit to monitor the discharge area ofsaid roller unit for freedom of said leather piece therefrom.
 13. Thedevice according to claim 12, wherein said detector device isoperatively connected to said drive control means.
 14. The deviceaccording to claim 12, wherein said detector device is operativelyconnected with said return control activation of said drive controlmeans.
 15. The device according to claim 12, wherein said detectordevice is operatively connected to said drive control means andinterrupts return travel movement in progress until the discharge areaof the roller unit is cleared of emerging material by stopping thegripping means in an assigned waiting position.
 16. The device accordingto claim 1, further comprising means for moving said gripping means in aforward and reverse direction and at least one gripper position detectorfor monitoring the forward or reverse movement of said gripping means.17. The device according to claim 16, further comprising at least oneadjustable-position gripper position indicator.
 18. The device accordingto claim 17, wherein said gripper position indicator is in operationalreturn travel activation connection with said drive means.
 19. Thedevice according to claim 16, wherein said gripper position detector isin operational return travel activation connection with said drivemeans.
 20. The device according to claim 1, wherein said gripping meanshas at least one pricking element that acts on said leather piece. 21.The device according to claim 20, further comprising a leather guidingroller located at said work station outlet side, wherein said prickingelement is mounted on the circumference of said leather guiding roller.22. The device according to claim 20, wherein said pricking elementincludes a means for switching said element from an active state inwhich said element is applied to said leather piece and an inactivestate in which said leather piece is released.
 23. The device accordingto claim 22, wherein said element switching means comprises apositioning device synchronized with the passage of the leather.
 24. Thedevice according to claim 22, further comprising a work stationincluding a pressure roller unit and a discharge roller having acircumference, the work station located in advance of the dischargeunit, wherein the gripping means is mounted on the discharge rollercircumference and wherein the pressure roller unit has a transfer pointlocated on the discharge roller circumference.
 25. The device accordingto claim 24, wherein when the pricking element passes by said transferpoint, the switching means is activated to move said pricking elementbetween the active and inactive states.
 26. The device according toclaim 21, further comprising a leather guiding roller having acircumference, wherein a plurality of pricking elements are mounted in agridlike pattern distributed over said leather guiding rollercircumference.
 27. The device according to claim 26, wherein saidplurality of pricking elements extend in a row along the generallylongitudinal length of said leather guiding roller, and wherein saidplurality of pricking elements can be switched together between saidactive and inactive states.
 28. The device according to claim 27,further comprising a reversal device for activation and deactivation ofthe pricking elements.
 29. The device according to claim 28, whereinsaid pricking elements are movable between said active and inactivestates, and wherein said reversal device includes at least one bellowselement that may be charged with and relieved of hydraulic fluid andthat acts on the pricking elements in the direction of movement.
 30. Thedevice according to claim 28, further comprising a spring operating onsaid pricking elements, wherein said pricking elements are movablebetween said active and inactive states, and wherein said prickingelements are placed in tension in the direction of said inactive stateby said spring.
 31. The device according to claim 20, wherein said atleast one pricking element is a needle.
 32. The device according toclaim 21, further comprising a pneumatic reversal device for saidpricking element, and further comprising a compressed air storage unitin the body of the roller and connected to a compressed air deliveryline.
 33. A continuous-operation device for the treatment of leather andsimilar materials, comprising:a work station including a roller unitincluding a pair of rollers and through which said leather piece ismoved, said work station including an inlet side and an outlet side, aconveyor belt upon which said leather piece is moved, said conveyor beltextending form said inlet side and through said work station to saidoutlet side, stripping means for removal of said leather piece from oneroller of said pair of rollers as said leather emerges from said workstation outlet side, said stripping means being connected to said workstation outlet side for releasing the emerging material from theconveyor belt, said stripping means having at least one compressed airnozzle directed toward the emerging edge of material.